HOW'D IT GET THERE THEN?: A deep hole in an Austrian field was discovered by a farmer looking his cat. A UFO was believed to be burried 25 feet beneath the ground there. (Photo: Life's Little Mysteries)

According to news reports, an Austrian farmer discovered a mysterious, deep, perfectly round hole that apparently had appeared in his field overnight. And, of course, extraterrestrial activity was assumed.

Farmer Franz Knoglinger discovered the hole while looking for a lost pet. In an interview with the Austrian Times newspaper, Knoglinger said: "I was looking for our family cat, Murlimann, when I noticed the hole. I didn't know how deep it was, so I dropped the stone down there and heard a metallic clunk. From the time it took for the stone to reach the bottom, I realized it was very deep."

Intrigued, Knoglinger used a rope to lower a magnet into the hole, and he concluded that whatever was at the bottom was metallic. This only deepened the puzzle, and soon the mystery drew local, national and, finally, international attention. Curiosity-seekers, geologists and UFO buffs flocked to the farm to see the hole for themselves. A buried UFO became a favorite explanation.

A few clues shed some light on the mystery. If the hole was indeed perfectly round, then the obvious source was a drill. In fact, the hole's perfect roundness would make it less mysterious, if anything, because drills leave round holes. A perfectly square, rectangular, or even oval shape would be more extraordinary.

Perhaps a more interesting question was why, of all the possible explanations — an abandoned well, a long-forgotten underground storage tank — the idea of an underground extraterrestrial spacecraft was the one Knoglinger and others focused on. [7 Things that Create Convincing UFO Sightings]

Part of the answer is that an extraterrestrial craft has become a default explanation in recent years for any large unknown (and presumably round and/or metallic) object. For example, a large round object was recorded on sonar on the ocean floor by a Swedish archaeology team last year. The image has not been confirmed as real (and many experts suspect it's actually a false reading), but by far the most popular explanation is that the round object is a spacecraft. Human imagination almost always creates far more exotic and interesting possibilities than reality can provide, and anything just out of reach, be it deep underwater or underground, can conjure visions of alien spaceships.

The case in Austria stumped many until a local historian decided to do a bit of digging — not in the dusty field but in the local land-use archives. It turns out the hole had not appeared overnight as Knoglinger assumed, but had been there for decades. In fact, a half-century ago an oil company had drilled there looking for oil. A large metal drill bit became stuck and broke before workers could find anything, so they left the drill bit at the bottom of the hole and never bothered to fill it in. That's what attracted the magnet dropped down to the bottom: not a spaceship but a large metal bit stuck in rock.

Over the years the area became farmland and people stopped noticing the hole, either because it had been covered by grass or a piece of wood or simply because, with the advent of modern farming machinery, there were fewer people working in the field.

As for the missing cat, it was eventually found hiding in a cupboard.

Benjamin Radford is deputy editor of Skeptical Inquirer science magazine and author of Scientific Paranormal Investigation: How to Solve Unexplained Mysteries. His Web site is www.BenjaminRadford.com.